Remove non-functional code coverage badge for now

README.md

@@ -3,7 +3,6 @@
 [![Latest version](https://img.shields.io/crates/v/askama.svg)](https://crates.io/crates/askama)
 [![Build status](https://api.travis-ci.org/djc/askama.svg?branch=master)](https://travis-ci.org/djc/askama)
 [![Windows build](https://ci.appveyor.com/api/projects/status/github/djc/askama?svg=true)](https://ci.appveyor.com/project/djc/askama)
-[![Code coverage](https://codecov.io/gh/djc/askama/branch/master/graph/badge.svg)](https://codecov.io/gh/djc/askama)
 [![Chat](https://badges.gitter.im/gitterHQ/gitter.svg)](https://gitter.im/djc/askama)
 
 Askama implements a template rendering engine based on Jinja.